So I had a local guy who was pretty desperate for some help on his setup getting it to idle and return to idle. He already had 2 good tuners before me try and fail to get it to act right. He is an ASE mechanic with ~25 years of experience and in talking to him I couldnt think of anything mechanically to try that he didnt try and replace already, at least once.
Build details are a 2007 yukon with a LY6 6.0 DOD/VVT delete, cam is a comp 218/230 106 which is pretty aggressive but should be doable. Stock intake and TB. Replaced TB and MAF multiple times. New fuel pump, all new sensors, new plug wires, new coils, inspected entire injector and coil harness. Only thing I am suspect of are the injectors which were new "5.3L flex fuel injectors" but part number came up as a trailblazer. I pulled the injector data from a repository file, but even if it wasnt exact it should be closer than it acts. Temp gun says all the runners are about the same.
At 1200rpm and up engine runs great, it just refuse to idle or return to idle or start smoothly. I tried all sorts of combinations of more idle air, less idle air, more timing, less timing, and nothing I did made it behave. Would start and flare if I held pedal down on next start attempt to clear it and would stay running as long as I gave it some throttle, but in 3 hours of messing with it I only got it to idle on its own exactly once.
The attached file is the one I started with that originally came with it (That runs good just wont start and idle). All of the logs are idle attempts.
I'm emotionally invested in this thing at this point and kind of at a loss. He said it used to run ok but gradually got worse so he started replacing parts and its never gotten better. Let me know if you have any ideas or suggestions. I said to replace injectors with some truly stock ones for that engine since thats the only thing I can kind of point to. Short of replacing the cam I am not sure what else to try.
It almost sounds like a mechanical issue. Have you checked it for vacuum leaks? You might take a look at the plugs and see if there are any indicators of fouling or misfires.